Method of erecting bridges



March 22, 1932. 3. 5. E. LARSSON METHOD OF ERECT ING BRIDGES Filed Sept. 15, 1928 1 In! I. v ZOFUMNM 02550 IFUZMJ L o g ILluzuJ .(Z-IL DUQZMLIXM L fig I Inventor.-

Patented Mar. 22, 1932 1 UNITED STATES PATENT OFFICE CARL GUSTAF EMIL LARSSON, F PLAINFIELD, NEW JERSEY METHOD OF ERECTING BRIDGES Application filed September 15, 1928. Serial No. 306,130.

This invention relates to the building of bridges across wide waterways and more particularly to bridges having a series of long, heavy spans, such as bridges for spanning rivers of great width.

l/Vhen a wide waterway is to be crossed by a bridge, it usually is economical to build the bridge in several spans, with intermediate piers. When the water is deep the bridge must be built high above the water to take bridges, wherein the use of false-work in erecting the bridges is avoided or greatly lessened, the difficulties ordinarily met with in erecting bridge spans over waterways of great depth are avoided and overcome, and whereby the cost of erection is very materially decreased.

7 Other objects of the invention will be made apparent hereinafter in the detailed description, and be particularly pointed out in the appended claims.

Referring now to the drawings forming part of this specification, Figure l is a diagrammatic side elevation of a bridge, illustrating novel features in the method forming my invention.

Figure 2 is a similar side elevation, showing other features of my improved method.

Figure 3 is a side elevation of a portion of a bridge showing further features of the novel method forming my invention.

Figure 4 is a plan showing details in the construction of one form of telescopic bottom chord adapted for use in carrying out my invention.

Figure 5 is an end elevation of the telescopic bottom chord of Figure 4.

In the accompanying drawings, the letter A denotes, in a general way, the bridge piers which are shown built up on the bed of a river or wide stream, and B, in a general way,'the series of bridge spans of which the bridge structure is formed.

The bridge piers A will be supported on suitable foundations and when the nature of the river bed C requires, the foundations for the piers will be built upon previously driven piles, or in any other approved manner. The piers A have an offset or step 2 in each side, at an intermediate point in the height thereof, for a purpose later described.

In building bridges like that shown in Figure 1 by my improved method, the false-work necessary to support one ofthe spans will be built alongshore, where the river is comparatively shallow, at or near the bridge site. As various ways of building such false-work, usually of wood, are old and well known, it is not shown and will not be further described.

In designing the bridge of Figure 1, one of the spans, generally one of the two shore spans and in this case the deck span B will be made somewhat shorter than the others and of a length which permits it to be securely mounted on the offsets 2 of any two adjoining piers A, except the pair on which it is eventually mounted in completing the bridge. The other spans will be of uniform, or substantially uniform, length.

This short deck span will first be erected on the false-work previously built off shore in the usual well known manner and after being assembled, will be transferred to pontoons or barges 3, 3 or similar floating craft. In building the false-work provision will be made for positioning the pontoons to receive the spans 13. The span laden pontoons will then be floated or towed into position to bring the short span B lengthwise opposite the gap or opening between the piers A and A When not high enough, the span will be blocked up on the pontoons to permit of its being moved between the pair of piers A A It will then be lowered until its ends rest on the oflsets 2 of these piers, or on the bents 4 when the offsets 2 are under water, as shown in Figure 1.

The pontoons may then be removed or may remain in place until needed in removing the span B 7 7 Generally, the oflisets 2 in the sides of the piers are below the level of the water in the river over which the bridge is to extend and, when necessary the height of the oifsets relative to the tops of the piers will-be carefully determined in order to locate the top ofthe span B at theelevation required for the use to which it is putwhen mounted on the'oifsets or steps 2 in the pier sides.

To bring the top of the span 'B to the dc sired height when supported on the ofi'sets 2, the bents 4 will be placed between the ends of ,thecrspans' B and top of the ofisets 2, as is being moved by meansof the pontoons into position between the piers A and A is mounted on the ,ofisets 2, 2 of theseEpiers in the same way as has beendescribed. The span B yis then again used-Lin lieu of the usual false-work tosupport thespan B while it is ibeingzerected in place on the piers A", A.

The deck span B also willbe used in erect- ;i'ngthe lifting span B ofthe bridge of Figure '1 when considered necessary or desirable, in the same way as has been described. Thedeck s an B is then transferred from I theofisets o the piers to the pontoons 3, 3

ill

and ,isfcarried by the pontoons into position qon'its piers A, A where it remains permanently. v

Onaccount: of its being longer than the distance ,face to :face of the-piers A A,it will be necessarygtoraisethe span B on the pontoons high enough :fojr'it to be moved into position above the piers on which it is then placed to completejthezerection ofithe new riverspans o'f-othegbridge. The approaches 6,1 6 will then be erectedin the usual manner, in completing the bridge of Figure 1.

Erequently itis vfound necessary or expedi- :Qnt in designing such bridgesto make all of :thiefipans ofthe same length or of so nearly uniform length that no one of them will be short enough to be positioned on the offsets or stepsofthepiers for use in erecting the other ,spans, as shown for example in Figure 2.

- Insuch;case, the end panels 7, 7 of one span B will the vdistorted when erecting it on the v,false-work so .as to shorten the overallzlength 10f this ispanenough for it to be used in the same way and for the same purpose as the shortspan B 'is used in erecting the bridge shown in Figure 1. I

' In distorting the end members of the span B to temporarily shorten its overall length 7 enough for it to be mounted on the offsets V of adjoining piers the end members of the bottom chords 9 of the trusses forming the span B will be made to telescope in the manner shown in Figures 4 and 5, and (when assembling this span on the false-work on which it is erected, the telescopic members 10, 11 will be secured in telescoped'or shortened position by bolts 1 2 whichext'end through registering holes in the telescopingmembers 10 and 11. (See Figure 4.) The end members 13 ofthe top chords of the trusses forming this'span being pin'connected their outer ends will :be swung downwardly out of normal position and will be connected by ins ,inthe'louter ends of the shortened mem rs 10;o f:the bottom chords so iaszto form theends of the span as shown dotted in Figure ,2.

After the shortened span 513 has been erected on the. false-work it is transferred to the' pontoons 3,;3and is carried bytbe pongtoonsfinto position to bemountedon the offsets 2 of the ,piers A and A of Figure 2, in the way described in connectiongwith the bridge of'Figure 1. r c

i The spanB ofthe bridgeiof Figure 2 is then erected on top of ,thepiers A and A?, and is X supported on the distortedor shortenedg-span *B idll'ringits erection. On accountfof -the curved ;to;p chords of the span B9, :1 small amount of false-work will "be built on top of the span B, this beingdone while thespan is I onthe false-work on which it is erected or after beingcplaced 'in p sition between the piers A", At, as is ,rfoun'd most expedient. After ionce being built, it will remainon .top of the-span :13 until the other spans of the bridge have been'ereeted.

After the span B has been erectedzon the piers A, A the-shortened span is :then successively moved, by meansof the pontoons,

into position and transferred :touthe ofisets on thepiers A and A A and A, A andAfl in ereeting the spans B, B :and B :by :the

method previously described.

After the other spans havebeen erected in place'with :the aid of the distorted or shortened span B, it is transferred :by the pon- -toons into position to be'put on top of'its piers A A.

The false-work on its top chords having now'been removed, the span B is raised on the pontoons until its shortened ends willswing clear of the'tops of the piers-on which it'is to rest, in the-mannershown in Figure 2, and the span is then lengthened. i

The bolts 12 are then removed from the telescopedend members "10, 1 1 of the bottom 1 chords 9 and the outer'panels'are successively extended by means of a hydraulicor Aether I jack 14 (shown diagrammatically in Figure 4) until the span 'B is restoredto its hill length.

The bolts 12 are then replaced in registering holes in the members and 11 of the bottom chords 9 and the span B is lowered until its ends rest on top of the piers A A The approaches will thenbebuilt and the roadway, foot walks and other parts of the bridge will be placed in position in completing the bridge.

It also is found necessary at times to make the series of spans of a bridge of such lengths that no one of them is adapted for use to support in the offsets of the piers the other spans while they are being erected on their piers, the spans being either too long or too short. When this necessity arises the lengths of the various spans will be proportioned so that one of them, while too short to reach from the offset in one pier to that of the opposite pier, is long enough to nearly reach from one offset to that of the opposite pier. Nhen this condition arises a short span B can be used as a support for the other spans I3 while they are being erected by canting the b-ents 4, 4 outwardly and anchoring them to the piers, in the way shown in Figure 3.

The steps of the method used in erecting the bridge of Figure 8 with the short span B will be the same as has been described in connection with the bridge of Figure 1, other than canting the bents 4, as shown in Figure 3. The supporting bents 4 may be used with the distorted trusses as well as with the normal trusses.

In other cases an extension will be built on each end of the span B to make it of the desired temporary length while it is being used to erect the other spans B of the bridge of Figure 3.

The advantages of my invention will be readily appreciated by those skilled in the art. By the use of my improved method the necessity of building false-work between each pair of piers to support each span is avoided. The enormous cost of erecting false-work in very deep water or in swiftly flowing water is made unnecessary. The danger of the false-work being carried away by floods or by ice during the erection of the bridge is removed and the cost of erection of the bridge is materially decreased.

Modifications in the steps of my improved method may be made without departure from the invention, as defined in the appended claims.

I claim 1. In the erection of bridges, the steps of erecting a span of the bridge on false-work, moving the erected span into position between opposite piers of the bridge, supporting the span temporarily from said piers below the top supporting faces thereof and employing the temporarily positioned span to support a second span during the erection thereof on said piers, and then transferring the temporarily positioned span into position on other piers to form a component of the completed bridge.

2. In the erection of bridges, the steps of erecting a span of the bridge on false-work, moving the erected span into position between opposite piers of the bridge, supporting the span temporarily from said piers below the top supporting faces thereof and employing the temporarily positioned span to support a second span during the erection thereof on said piers, then transferring the temporarily positioned span into position between another pair of piers, and again employing the transferred span to support another span in the erection thereof on its piers, and finally positioning the temporarily positioned span on other piers to form a component of the completed bridge.

3. In the erection of bridges, the steps of assembling a span on false-work, transferring the span to offsets on opposite piers of the bridge below the top supporting faces thereof and employing said span to support a second span during the erection thereof on said piers between which the first span eX- tends, and finally transferring said first span in place on other piers to form a component of the completed bridge.

4. In the erection of bridges, the steps of erecting a span on false-work, transferring the assembled span to offsets on opposite piers of the bridge below the top supporting surface thereof, interposing supports between said offsets and span to bring the span to the desired elevation, and employing said span to support another span during the erection thereof on said piers between which the first span extends, and then removing said span and positioning it on other piers to form a component of the bridge.

5. In the erection of bridges, the steps of assembling one span of the bridge on false- .work, distorting the ends of the span to change its finished length, floating the distorted span between opposite piers of the bridge, transferring the distorted span to ofisets on said piers below the top supporting faces thereof, then erecting a second span above said distorted span and employing the distorted span to carry the weight of said second span during the erection thereof on the piers, removing said distorted span and then removing the distortion and positioning the span on piers to form a component of the completed bridge.

6. In the erection of bridges, the steps of assembling one span of the bridge on falsework, distorting the ends of the span to reduce the finished length thereof, floating the.

span between opposite piers of the bridge, transferring the distorted span to offsets on said piers below the top supporting faces thereof, erecting a second span above said distorted span and employing the distorted span to carry the weight of said second span j in the erection thereof on the piers, and then alternately removing said distorted span to a location between other, piers of the bridge andiemployingfit in erecting other s ans-f the bridge, and finally lifting the d storted span into positionabove and between oppositefpiers, increasing the length of the s an a by re-forming its distorted ends and t en the steps of assembling one span of bridge in sucha position that it may be readreadily span to reduce the finished length thereof,

ily oated, floating the assembled span between opposite piers of the bridge, supporting said assembled span on the piers between which it is floated, then erecting a second span abovesaid first named span and employing said first named span to carry the weightof said second named span during the erection thereof on the piers, removing said first named span and repeating said operations for successivespans of the bridge until ,said first named span only remains to be placed in positionon the piers, then floating I said first namedspan into position between the piers on. which it is to rest, and then finally liftingsaid first named span above the "piers on which it is to be mounted and mounting said span.

9. In the erection of multiple span bridges, the steps of assembling one span of the bridge in such aposition that it may be floated, distorting the ends of the floating'the span between opposite piers of the bridge, supporting said distorted span on the piers between which it is floated, then erectinga second span above said distorted span and employing said distorted span to carry the weight of said second named span in the erection thereof .on the piers, removingthe distorted-span and repeating said operation for successive spans of the bridge until said distorted span only remains to be placed in position on its piers, then floating said distorted span into position between its piers, and finallylifting said distorted span into position above and between its opposite piers,-increasing the length of said distorted span, and then lowering the lengthened span upon its piers to form a component of the completed bridge.

10. In the erectionof a bridge, the steps of adjacent piers, utilizing said temporarily 'positioneds an in lieu of false-workior the erection o apermanent s an on and between said piers, and then with rawing the temporarily positioned span andmo mg t toanother position and including it inthe bridge structure as a permanent art thereof.

In testimony whereof, have hereunto set my hand. a a I CARL GUSTAF EMIL LARSSON.

providing-a span, placing said span tempojrarily between and supporting the same on 

